Extending the limits of force endurance: Stimulation of the motor or the frontal cortex?

No effect of tDCS of the primary motor cortex on isometric exercise performance or perceived fatigue

“…While this variability has been well recorded for other behavioural paradigms (see Horvath et al,324 2014 and Parkin et al, 2015 for reviews), it is less acknowledged in studies of fatigue. However, 325 our results, in addition to others (Kan et al, 2013;Flood et al, 2017;Radel et al, 2017), indicate 326 that such variability is also present when tDCS is applied as an ergogenic aid. 327…”

“…It is 313 possible, therefore, that longer stimulation times are required to increase exercise tolerance. Ten We consider this unlikely, however, because others have also reported no effects in exercise 320 performance following 20 minutes of stimulation (Flood et al, 2017;Radel et al, 2017) . Instead, 321 it is far more likely that the present and previous failures to replicate the ergogenic effect of tDCS 322 simply represent the substantial inter-individual variability that exists in response to stimulation.…”

“…To 294 our knowledge, this is the second pre-registered study to find no effect of tDCS on isometric 295 exercise performance. Radel et al, (2017) also reported no effect of 2 mA high definition-tDCS of 296 the primary motor cortex on upper limb isometric exercise performance. The small effects we 297 report here are also similar to the standardized effects reported by Radel et al, (2017).…”

“…Radel et al, (2017) also reported no effect of 2 mA high definition-tDCS of 296 the primary motor cortex on upper limb isometric exercise performance. The small effects we 297 report here are also similar to the standardized effects reported by Radel et al, (2017). The results 298 of these two pre-registered studies, plus other exploratory studies (Kan et al, 2013;Flood et al, 299 2017) and recent systematic reviews (Holgado et al, 2019;Machado et al, 2019), suggest that, 300 contrary to recent proposals (Angius et al, 2017;Edward et al, 2017), tDCS does not enhance 301 exercise performance, at least not for a sustained isometric contraction.…”

The effects of transcranial direct current stimulation on objective and subjective indexes of exercise performance: a systematic review and meta-analysis.

“…For example, Angius et al [9] and Vitor-Costa et al [30] found an improvement in a cycling TTE test after anodal tDCS and Cogiamanian et al [21] also found a Consequently, the performance benefit could be mediated by an increase in motor cortex excitability after the anodal stimulation. However, contrary to these findings, Radel et al [40] found no improvement in performance in a TTF arm flexion or changes in cerebral O 2 Hb measured with near infrared spectroscopy and Holgado et al [41] failed to find any change in the electroencephalography brain electrical activity at rest or during exercise in a 20-min cycling time-trial after anodal stimulation of the prefrontal cortex. These mixed results are a clear sign of the variety of outcomes and converge to the conclusion that the effects may be small and possibly biased.…”